The current art teaches that liquefied natural gas (LNG) can be stored in a variety of vessels and tanks. Compressed natural gas (CNG) can be stored in higher pressure rated tanks. Problems exist in current storage processes for small vessels that have to travel long distances. A need exists for storage sites underground that provide access to the CNG and also protect the CNG itself.
Compressed natural gas can be transported by way of a barge or above deck on a ship. CNG is typically cooled to a temperature around −75 degrees Fahrenheit at a pressure of around 1150 psi. The CNG is placed into strong, pressure vessels contained within an insulated cargo hold of a ship. Cargo refrigeration facilities are not usually provided aboard the ship even though the cargo is cool. A disadvantage of these ships is that they only travel short distances. If the distance to be traveled is long, the ship must not be delayed in unloading, or else the CNG bleeds off and the shipment is wasted. Current CNG storage systems have the problem of dealing with the inevitable expansion of gas in a safe manner as the gas warms during transport.
A need exists, therefore, for compressed natural gas storage systems that can contain large quantities at intermediate points on an itinerary, or at a remote location that contains refrigeration or sophisticated CNG containment systems.